1. Field of the Invention
In this aging society, there is an increasing need for providing appropriately designed shapes and sizes for medicines to be taken by elderly people without causing any swallowing problem. A poll on the shape and size of medicines good for elderly people conducted recently shows that while tablets are the best choice in terms of easy handling, they are accompanied by a problem of the difficulty of swallowing that elderly people experience because of their weakened ability for deglutition.
Apart from the elderly, there is also a strong demand for medicines that come in different shapes and sizes in order to meet the highly diversified life styles of people in this modern society. For instance, there is a strong demand for medicines that do not require water for swallowing and those infants can take in without difficulty. From this point of view, efforts have been paid recently to develop tablets capable of quickly disintegration in the oral cavity.
This invention relates to a method and an apparatus for manufacturing a tablet capable of quick disintegration in the oral cavity that is adapted to be shaped by a simple process following a punching process.
2. Prior Art
In view of the above identified applications, a tablet of the type under consideration should disintegrate as quickly as possible in the oral cavity once it is orally administered, typically in 15 seconds.
While various methods have been proposed for manufacturing tablets capable of quick disintegration in the oral cavity, any method that requires the use of a specifically designed apparatus entails high manufacturing cost to significantly push up the price of the final product. Additionally, the use of one or more than one particular additives can give rise to problems in terms of the quality and the stability of the produced medicinal products. Therefore, it is preferably that tablets capable of quick disintegration in the oral cavity are made of materials that are popularly used as pharmaceutical excipients and that the method for manufacturing such tablets is very simple.
Japanese Patent Application Laid-Open No. 8-291051 titled as "Method for Manufacturing a Quickly Soluble Tablet and a Tablet Manufactured by such a Method" discloses a process of manufacturing a quickly soluble tablet that comprises three steps of low pressure punching, moisturizing and drying. According to the above patent document, low pressure punching refers to an operation of punching out a tablet with a minimal level of pressure necessary to make it keep its form when moving to the next moisturizing step. The specific pressure level for the punching step described in the patent document is between 0.1 and 2.0 t/cm.sup.2, preferably between 0.2 and 1.0 t/c m.sup.2. In an example described in the patent document, tablets were punched out under the pressure of 0.3 t/c m.sup.2.
According to Japanese Patent Application Laid-Open No. 8-291051, the disclosed method requires the use of a water-soluble binding agent as an indispensable ingredient for making the tablet punched out under low pressure maintain a certain level of hardness.
However, the use of a water-soluble binding agent as described in Japanese Patent Application Laid-Open No. 8-291051 can prolong the time necessary for the tablet to disintegrate in the oral cavity so that the ratio to which the agent is added should be minimized or, if possible, the use of such an agent should be totally avoided.
Additionally, the use of low pressure for punching out a tablet can give rise to a low porosity in the punched out tablet. The void or the fine spaces existing in a tablet normally allow saliva to infiltrate into the inside of the tablet and accelerate the disintegrate of the tablet in the oral cavity. Therefore, the porosity of a tablet that is designed to be capable of quick disintegration in the oral cavity significantly affects the time necessary for the tablet to disintegrate in the oral cavity. The porosity of a tablet produced by a method disclosed in Japanese Patent Application Laid-Open No. 8-291051 and under low punching pressure of 0.1 to 0.2 t/cm.sup.2 will be between 20% and 15%. On the other hand, for a tablet to be disintegrated in the oral cavity within 10 seconds, the porosity of the tablet should be not less than 20%, preferably not less than 25%, regardless of the ingredients and the size of the tablet.